I. Field of the Invention
This invention pertains to gripper arm apparatus, particularly gripper arms employed in collating machines such as an insertion machine, and to methods of operating such machines which utilize gripper arms.
II. Prior Art and Other Considerations
U.S. Pat. No. 4,634,107 entitled GRIPPER ARM AND METHOD OF OPERATION, commonly assigned herewith and incorporated herein by reference, discloses a gripper arm wherein a movable gripper jaw is actuated by a solenoid acting through a linkage to engage articles between the movable jaw and another jaw, and thereafter to release the articles. The solenoid is assisted by biasing means which is preloaded to facilitate the application of a desired holding force on articles engaged between the jaw members. When the solenoid is not actuated, the gripper jaws are spaced apart from one another by a gap or distance which is a function of such factors as the length of the jaws from a pivot point and the impact of the effective length of the linkage (taking into consideration the effect of the biasing means when the solenoid is not activated) upon the positioning of the movable gripper jaw. When the solenoid is activated, it is contemplated that the gripper jaws would touch one another if an article such as an insert were not gripped therebetween.
In operating collating or insertion machines employing gripper arms such as that described above, in differing batches or runs it is often required that a gripper arm engage and release articles (such as sheets) of a variety of different thicknesses. For example, during a first batch an insert hopper associated with a gripper arm may be loaded with inserts of very thin paper, but during a second batch the same insert hopper may be loaded with inserts of much thicker paper stock. Despite the change in insert thickness from batch to batch, for the prior art solenoid-actuated gripper arms the gap separating the gripper jaws when the solenoid is not activated remains essentially uniform.
For some embodiments of prior art solenoid-actuated gripper arms the jaws may not be sufficiently separable to accommodate and then engage very thick articles therebetween. It would be highly desirable, therefore, to provide a gripper arm which could accommodate thick articles between its jaws without having to change the dimensions of basic structural items such as the length of the jaws, the length of the linkages, and the length of the solenoid plunger stroke.
U.S. Pat. Nos. 3,744,787 and 3,885,780 to Morrison show prior art method and apparatus employing a plurality of adjustment screws for adjusting a gripper arm to accommodate inserts of different thicknesses. The Morrison patents, predating the advent of the solenoid-actuated gripper arm, show apparatus not optimally suited for operation with the solenoid actuator and linkage of the incorporated application.
In view of the foregoing, it is an object of the present invention to provide a gripper arm and method of collating machine operation wherein the distance separating the jaw members of an electrically actuated gripper arm is selectively adjustable.
Another advantage of the present invention is the provision of an adjustable gripper arm wherein an adjustment for changing the distance separating gripper jaw members is easily made by a single operation.
Yet another advantage of the present invention is the provision of method and apparatus for adjusting the position of gripper jaws of a solenoid-actuated gripper arm.
An advantage of the present invention is the provision of an adjustable gripper arm having means for indicating the degree of a selected adjustment.
A further advantage of the present invention is the provision of means for apprising an operator (standing on the backside of a gripper arm) that the gripper jaws (located on the front side of a gripper arm) have been sufficiently adjusted for the articles to be engaged between the jaws.